In some medical procedures, such as intraoperative autotransfusion, blood lost by a patient is collected or salvaged to make it available for reinfusion back to the patient. Prior to reinfusion, the collected blood is cleaned to make it safer for the patient. Typically, red blood cells are separated from plasma that contains undesirable elements, such as fat, activated clotting proteins, anticoagulant, activated platelets, coagulation by-products, cellular debris, and free hemoglobin (Hgb). The red blood cells are reinfused back to the patient.
In some autotransfusion systems, the components of the blood are separated using a centrifuge bowl. Salvaged blood is put into the centrifuge bowl through an inlet tube and rotation of the centrifuge bowl causes the red blood cells, which are the heaviest cellular components of blood, to be propelled outward, compacting the red blood cells against the wall of the centrifuge bowl. Other cellular components, such as white blood cells and platelets, are arranged in a thin layer, referred to as a buffy coat, directly adjacent the concentrated mass of red blood cells. The plasma, which contains the undesirable elements, is situated in a layer nearer the axis of rotation than the buffy coat. As filling continues, more of the heavier components, i.e. the red blood cells, are pushed inwards, nearer to the axis of rotation, which pushes the lighter plasma, such as fat, out of an outlet at the top of the centrifuge bowl. The introduction of salvaged blood into the centrifuge bowl ceases once the centrifuge bowl has substantially filled with red blood cells.
Next, a washing solution, such as a saline solution, is pumped into the centrifuge bowl to wash the blood. Often, the washing solution is added at a steady flow rate to gradually take the place of the plasma and other unwanted elements that are expelled through the outlet from the centrifuge bowl. After washing, the centrifuge bowl contains concentrated red blood cells and washing solution, which can be collected in a reinfusion pouch or bag and made available for reinfusion back to the patient.
Manufacturers continuously strive to provide increased hematocrit (HCT) levels and decreased levels of the undesirable elements in the collected blood for reinfusion back to the patient.